This study analysed the capacity of the Catalan and Spanish versions of the Bilingual Aphasia Test (BAT) to distinguish between normal and pathological aging. Both versions of the test were administered to 45 bilingual subjects: 15 healthy aging subjects, 15 patients with mild cognitive impairment and 15 patients with Alzheimer's disease. To explore which combination of subtests was best suited to differentiate the three study groups, stepwise discriminant analyses were performed using each version of the Bilingual Aphasia Test separately and together. The percentages of properly classified subjects were as follows: 93.3% when the Spanish version was administered, 88.9% when the Catalan version was administered and 95.6% when both versions were used. The subtests that best classified the subjects were of the lexical-semantic type but also related to metalinguistic capacity and language organisation skills. The performance of each group in Catalan and Spanish was more similar than different. (Contains 11 tables and 5 figures.)